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1324Re: NewReno and the 2001 Revision

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  • Rick Jones
    Sep 24, 1998
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      Tom Henderson wrote:
      >
      > On Wed, 23 Sep 1998, Kacheong Poon wrote:
      >
      > > Can you describe what you meant by SACK with Reno and SACK with NewReno? With
      >
      > First, let me define NewReno for the purpose of this discussion. NewReno is
      > Reno with the following changes:
      > i) define a variable (snd_recover) that is set to snd_max upon entering fast
      > recovery. When snd_una reaches snd_recover, the fast recovery phase is
      > considered to be over.
      > ii) if a partial cumulative ack is received (ti_ack < snd_recover), retransmit
      > the next segment beyond ti_ack, deflate snd_cwnd by the amount of new
      > data acknowledged, add back one segment to snd_cwnd, and send a new segment
      > if permitted.
      > iii) if a new ack is received with (ti_ack >= snd_recover), set snd_cwnd to
      > min(snd_ssthresh, amount of outstanding data in the network + 1 segment)
      > and otherwise exit fast recovery as in Reno.

      I'll have to ask the guys currently supporting MPE/iX, but I think that
      the behaviour described in i has been present in the MPE/XL (now iX) TCP
      stack since we implemented congestion control and avoidance. ii has been
      present in that the next segment after the ACK would be sent, but I do
      not recall new data being allowed. that stack would then start from a
      cwnd of 1 upon iii.

      At the time (89-90ish) it worked pretty well for aggregate file
      transfers over 9600 baud dial-ups.

      rick jones
      --
      these opinions are mine, all mine; HP might not want them anyway... :)
      feel free to email, or post, but please do not do both...
      my email address is raj in the cup.hp.com domain...
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